The present invention relates to a retainer for a rolling bearing such as a deep groove ball bearing used in a motor requiring low vibrations and low noises.
A deep groove ball bearing, which is used to support a bearing portion or a rotary portion in various rotary machines, comprises an inner ring having an inner ring raceway of a deep groove formed in the outer peripheral surface thereof, an outer ring disposed concentrically with the inner ring and having an outer ring raceway of a deep groove formed in the inner peripheral surface thereof, and a plurality of balls rollably interposed between the inner and outer rings. The respective balls are rollably held by a retainer, and lubricant such as grease and other kinds of lubricant oil are filled into a space between the outer peripheral surface of the inner ring and the inner peripheral surface of the outer ring, in such a manner that the inner and outer rings are allowed to rotate with respect to each other due to the rolling movements of the balls.
Here, as conventional examples of the above-mentioned retainer, there are known retainers which are disclosed in, for example, JP-A-9-144762 shown in FIG. 9 (which is hereinafter referred to as a prior application art 1), and JP-A-7-208482 shown in FIGS. 10 and 11 (which is hereinafter referred to as a prior application art 2).
Firstly, FIG. 9 shows a retainer 2 which is disclosed in the prior application art 1. This retainer is a crown-shaped member formed of, for example, synthetic resin by injection molding and comprises a plurality of pockets 4 formed in the proper positions thereof such as on the circumference thereof; and, on one side of the axial direction of each of the pockets 4, there is formed an annular-shaped base portion 6 and, on the other side of the pocket axial direction, there is formed an opening 8 set smaller than the diameter of a ball (not shown). The adjoining pockets 4 are separated by a pillar portion 10, a pair of elastically deformable pawls 12 respectively extend in an arc-shaped manner from the leading end of the pillar portion 10 and cooperate together in defining the opening 8, and the opening 8 is set smaller than the diameter of a ball (not shown). And, the peripheral edge of the pocket 4 is formed in a concave-shaped spherical surface and, on the leading-end-side area of each pocket 4, there is provided a projecting portion 12a. The projecting portion 12a has an arc-shaped section and is disposed along the width-direction curvature of the peripheral surface of the pocket 4. Due to provision of the projecting portion 12a, when a ball is stored in the pocket 4, the projecting portion 12a is elastically contacted with the ball, thereby restricting the self-oscillation of the ball.
Also, FIGS. 10 and 11 show a retainer 16 which is disclosed in the prior application art 2. In the case of the retainer 16, between a pair of pawls 19 disposed on one side X of the axial direction of the retainer 16, there are interposed a plurality of pockets 18 at proper positions such as on the circumference thereof having openings 18a, while the dimension of the opening width W of each of the openings 18a is set smaller than the diameter D of a ball 20.
Each pocket 18 includes two side wall surfaces 18b respectively disposed on the two sides of the circumferential direction thereof and a bottom wall surface 18c disposed opposed to the opening 18a of the pocket 187 and, the side wall surface 18 is formed as a concave-shaped spherical surface having a radius of curvature R1 the center of curvature of which is a point O1, while the bottom wall surface 18c is formed as a flat surface extending at right angles to the axial direction of the pocket 18. The radius of curvature R1 of the side wall surface 18b is larger than the radius D/2 of the ball 20. And, the center O2 of the ball 20 in the intermediate portion thereof (where the ball 20 is situated in the center of the pocket 18 and is contacted with neither the side wall surfaces 18b nor the bottom wall surface 18c) is shifted by a dimension S toward one side X of the axial direction of the pocket 18 from the center of curvature O1 of the side wall surfaces 18b, and the ball 20 is shifted toward the opening 18a side. The retainer 16 can be moved from this shifted state by a dimension A toward the other side Y of the axial direction thereof and by a dimension B in the circumferential direction thereof until it is contacted with the ball 20 and, at the same time, can be moved by a dimension C toward one side X of the axial direction until the bottom wall surface 18c is contacted with the ball 20.
However, in the prior application art 1, in the process in which the retainer 2 is formed by injection molding, in a step of removing a metal mold, the projecting portion 12a interferes with the metal mold, which makes it difficult to manufacture the metal mold. Also, when storing the ball into the retainer 2, while pressure contacting the ball against the leading ends of the pair of pawls 12 disposed in the openings 8 to thereby spread out them elastically, the ball is stored from the opening 8 into the pocket 4. Such provision of the projecting portions 12a on the pair of pawls 12 reduces the dimension of the opening 8, thereby raising a fear that the pawls 12 can be damaged or broken when pressure contacting the ball 20 with the leading ends of the pair of pawls 12.
Also, in the prior application art 2, when the retainer 16 is moved toward one direction X of the axial direction in FIG. 11, there is eliminated a clearance for holding the lubricant held between the bottom wall surface 18c and ball 20 to thereby worse the lubricating state of the retainer 16, which increases sliding friction between the bottom wall surface 18c and ball 20. This raises a fear that the pawls 19 can be self-oscillated, which makes it impossible to reduce the noises of the retainer to a satisfactory degree, so that its improvement has been desired.
The present invention aims at eliminating the above-mentioned drawbacks found in the conventional retainers for a rolling bearing. Accordingly, it is an object of the invention to provide a retainer for a rolling bearing which is structured such that, in the leading end portions of the pawls defining the pocket, there are not provided the projecting portions having disadvantageously influences on the manufacture of a metal mold for injection molding the retainer and on the storing operation of the ball or rolling element into the retainer, and also which can restrict the axial-direction movement of the retainer with respect to the rolling element to thereby be able not only to prevent generation of noises in the retainer but also to enhance the lubricating property of the retainer.
In attaining the above object, according to the invention, there is provided a retainer for a rolling bearing, formed in a circular-ring shape as a whole, comprising: a plurality of pockets formed at a plurality of portions thereof in the circumferential direction thereof for storing and holding rolling elements with the pocket surfaces of the pockets; and, a plurality of openings respectively formed on one side of the axial direction of the respective pockets, each of the openings having an opening width set smaller than the diameter of the rolling element, wherein the ratio of an axial clearance xcex4, which is formed between the rolling surface of the rolling element in the above axial direction and the pocket surface, to the diameter Da of the rolling element is set in the range of xcex4/Da=xe2x88x920.01xcx9c0.02 (i.e., xcex4/Da is in the range between xe2x88x920.01 and 0.02).
In case where the value of xcex4/Da exceeds 0.02, when the retainer is going to move in the axial direction with respect to the rolling element, there is a fear that the axial clearance xcex4 increases excessively to cause the rolling element to be collided with the inside pocket surface of the opening and the pocket surface of the bottom portion of the pocket with a large force, thereby increasing the noise level. On the other hand, in case where the value of xcex4/Da is smaller than xe2x88x920.01, the axial clearance xcex4 between the rolling surface of the rolling element and the pocket surface decreases, thereby raising a fear that the dynamic torque can be increased suddenly.
However, as in the present invention, in case where the ratio of an axial clearance xcex4, to the diameter Da of the rolling element is set in the range of xcex4/Da=xe2x88x920.01xcx9c0.02, the inside pocket surface of the opening and the pocket surface of the bottom portion of the pocket restrict the movement of the retainer in the axial direction thereof to thereby be able not only to reduce the collision force between the rolling element and the pocket surfaces of the retainer but also to obtain a sufficiently large lubricant collecting portion, which can prevent an increase in the dynamic torque and noise level.
Also, in case where the pocket surface comprises a pair of first pocket surfaces respectively formed inside the opening and a second pocket surface formed between the two first pocket surfaces, and the center of the radius of curvature of the first pocket surface is shifted in the axial direction or in the circumferential direction with respect to the center of the radius of curvature of the second pocket surface substantially coincident with the rotation center of the rolling element, when the rolling element is contacted with the inner walls of the opening, there is formed a relatively large lubricant collecting portion in the circumferential direction between the rolling element and first pocket surfaces, so that not only the above-mentioned dynamic torque and noise level can be prevented from increasing but also the lubricant can be made easy to flow into the pocket and to be held therein.
Specifically, in case where the radius of curvature of the first pocket surface is set at a value larger than the radius of curvature of the second pocket surface, the center of curvature of the radius of curvature of the first pocket surface is shifted from the center of curvature of the radius of curvature of the second pocket surface toward the opposite side to the opening in the axial direction, and the inflection point heights of the first and second pocket surfaces are set so as to coincide with each other, there can be formed a relatively large lubricant collecting portion in the circumferential direction of the retainer.
Also, in case where the radius of curvature of the first pocket surface is set at a value smaller than the radius of curvature of the second pocket surface, the center of curvature of the radius of curvature of the first pocket surface is shifted in the circumferential direction with respect to the center of curvature of the radius of curvature of the second pocket surface, and the inflection point heights of the first and second pocket surfaces are set so as to coincide with each other, the manner of embracing the rolling element by the pocket surface on the opening side can be set freely.
Further, in case where the radius of curvature of the first pocket surface is set at a value equal to the radius of curvature of the second pocket surface, the center of curvature of the radius of curvature of the first pocket surface is shifted from the center of curvature of the radius of curvature of the second pocket surface toward the opposite side to the opening in the axial direction, and the inflection point heights of the first and second pocket surfaces are set so as to coincide with each other, when designing a metal mold for forming the retainer by injection molding, the origin can be determined simply, thereby being able to facilitate the manufacture of the metal mold.